I'm hoping to cover my air fare

Mel Smith's film work has made him millions. But one role has tempted him back on stage after 20 years. Dominic Cavendish meets him

It's two decades since Mel Smith's prime-time heyday, when millions watched him and Griff Rhys Jones, a fellow alumnus from Not the Nine o'Clock News, mine their double-act for all its comic worth in Alas Smith and Jones.

Yet you'd still be able to pick him out in a crowd. Looks-wise, he hasn't much changed. The baby-face jowls, protruding lower lip and pudgy physique are dead giveaways: like Tony Hancock, say, or Sid James, Smith has the kind of features that don't allow him to go undercover for a minute.

Except that they do make a very good match for the bulldog looks of Winston Churchill - a likeness seized upon by Irish journalist and author Mary Kenny, who asked Smith whether he fancied bringing the political colossus back to life for a play she'd written about Churchill's extraordinary encounter with the Irish nationalist leader Michael Collins.

Premièring at this year's fringe, Allegiance is set in Churchill's London residence, Sussex Gardens, in December 1921, at a moment when negotiations over the Anglo-Irish Treaty have stalled.

Churchill, then Colonial Secretary under Lloyd George, seized the initiative and extended the hand of personal hospitality to a man regarded as the mortal enemy of British interests.

It was a gamble that paid off; a few years later, before his death - a violent consequence of the treaty's signing - Collins was reported to have said: "Tell Winston we could never have done anything without him."

Smith, who was born in 1952, during the second Churchill administration, and is a long-standing admirer of Britain's wartime saviour - "Without him we'd have been sunk" - loved the play: "It taps into something that always fascinates me, which is what top people in the world say to each other once they're left alone."

Without hesitation, he signed up for what will be his first stage role for more than 20 years. He last starred as the cross-dressing Fancourt Babberly in the Victorian farce Charley's Aunt when Griff Rhys Jones pulled out through illness.

Smith's earliest allegiance was to the theatre. The son of a Chiswick bookie, he started off as a promising director, working at the Royal Court, the Bristol Old Vic and Sheffield Crucible during the '70s.

Now, after ages immersed in the worlds of TV and film, he is sworn friends with live performance again. "I'm going back to my first love," he says, smacking his lips with relish in the immaculately tended garden of his home in St John's Wood, north London, dotted with an endearing selection of animal sculptures.

It's not, he says, that he turned his back on the theatre - but force of circumstance shifted him on to a different career path. And it was the Edinburgh Fringe itself, scene of many of Smith's undergraduate forays during the late '60s and early '70s, that brought that about.

The future bigshot TV producer John Lloyd, then directing the Cambridge Footlights, caught Smith in a rival revue by the Oxford Theatre Group: "I did one sketch which John Lloyd said broke him up so much that he had to have me on Not the Nine o'Clock News. I played a man who sang, 'I am the very model of a modern major general,' and then went on to sing utter gibberish. It was pure verbal slapstick. It got plenty of laughs, though.

"When he rang me up a few years later and said: 'Do you want to be in a new satirical comedy programme?' the first thing I asked was, 'How much?', because I was broke. He said '£100 an episode.' I said: 'You're on.'"

That's probably about as much as he'll earn for his week-long return trip to the Fringe. "I'm hoping to recoup the air fare," he jokes. These days, though, he can afford to do things for love.

In 2000, he and Jones reaped a huge windfall when their production company Talkback - responsible for such TV comedy hits as The Day Today and Da Ali G Show - was sold for £62 million.

Others might have been tempted to retire, but Smith admits to restlessness. "I said to my wife [Pam, a former model], 'I need to do something to get me out of the house.'"

In the autumn, he's starring opposite Belinda Lang in a tour of a new comedy, An Hour and a Half Late, by French playwright Gérald Sibleyras, best known for the Olivier-winning Heroes.

Smith, who has adapted it himself, describes it as "a lighter version of Who's Afraid of Virginia Woolf?". After that, he'll direct a West End revival of Charley's Aunt, starring Stephen Tomkinson. Things have certainly come full circle.

Truth to tell, he says, the movie business had begun to drive him crazy. Despite an auspicious directorial debut with the hit Britcom The Fall Guy (1989) and scoring at the box-office with Bean (1997), starring his old chum Rowan Atkinson, the strains of film production have taken their toll.

He ended up seriously ill in hospital in 1999 after popping more than 50 Nurofen tablets. It was the culmination of a growing addiction to the pills. He said that the pressures of film work were a contributing factor, along with a desperate need to ease the pain caused by gout. "It was an incredibly silly thing to do, but it's all in the past now," he says.

The closest he'll come to substance abuse in Edinburgh is smoking a cigar, and his freedom to do so vexes him: the show might fall victim to Scotland's anti-smoking edict. "In the script, the cigar isn't just a prop," Smith fumes, puffing away on a Villiger.

"There's a whole palaver where Churchill offers Collins a cigar, and Collins gets out a packet of cigarettes and they have a joke.

It's the moment where they begin to relax. So it would be incredibly unfortunate if I wasn't allowed to light up. They could have a warning saying 'A third of a Romeo y Julieta will be smoked during this performance. If you find that offensive, f*** off!'"

Smith lets out a wonderful gun-blast of a guffaw, Churchillian to the core.